The Kiesel/Carvin Custom Shop has added chambered body option (CMB) to their CT624 and CT7 California Carved Top electric guitars.
Chambering the body can reduce the overall weight of an instrument by as much as a half-pound (a difference more important than it may seem after a few hours of playing/rehearsal). Cosmetically, there's no difference in versions with CMB and without, as the chambering is concealed under the top wood.
Many guitarists are always searching for the lightest instrument possible, and have even avoided quality tone woods such as mahogany and walnut because of the perceived weight issues. The CMB option makes it possible to order a guitar made from one of these heavier woods but that will still come in on the lighter side of the scale than the average instrument, which should be quite appreciable especially for extended sessions.